With COVID-19 outbreaks being whipped up for a fifth year, testing has emerged as a source of frustration once again.

Whereas obtaining a test was often difficult in early 2020, now the abundance of cheaper rapid kits in grocery stores and home medicine cabinets has led to a new concern — they don’t seem to work.

"When people tell me that their rapid antigen tests never turn positive, they’re usually talking to me because they’re frustrated,” says immunologist and epidemiologist Michael Mina.